A catalytic converter may convert undesired waste-gas components, such as HC, CO and NOx into less harmful components, such as H2O, CO2 and N2. To comply with increasingly stricter emission limit values, it may be desired that pollutant conversion be quickly applied in the three-way catalytic converter following a cold start of the combustion engine (of the internal combustion engine). Since the conversion may only set in above a minimum temperature, this minimum temperature should be reached as quickly as possible after a start.
To more rapidly heat a catalytic converter following a start, a burner located upstream from the catalytic converter may be used, which heats up the catalytic converter before and/or during and/or directly following an engine start. Using a burner for this purpose is discussed, for example, in German Published Patent Application No. 44 30 965.
By using a burner, an exhaust-gas heating effect may be produced without a feedback effect on the engine. A burner may have a separate combustion chamber upstream from the catalytic converter, and an external ignition source. The burner may function in that fuel, which is supplied via a fuel path, is mixed separately (i.e. in addition to supplying fuel to the internal combustion engine) with air that is supplied via an air path, and is ignited and burned by the ignition source. The burner's flame and its hot exhaust gases may heat up the downstream catalytic converter. The afore-mentioned document discusses that both burner air, as well as fuel are supplied to a burner nozzle via a fuel shutoff valve and a fuel regulator 34. Although the use of the term “regulator” may point to a closed-loop for correcting the fuel supply to the burner, it is believed that German Published Patent Application No. 44 30 965 does not describe a detection or measuring of the fuel quantity which is used to operate the burner. However, with a view to complying with optimal setpoint values for the firing of the burner and for a burner operation where the pollutant emission is kept as low as possible, as well as for a diagnostics of the fuel path, it may be desirable to know the absolute fuel quantity or the relative fuel quantity normalized to the burner-air quantity (the fuel/air ratio) at which the burner is operated.